VOR and reverse sensing

Hi all,

What is meant by reverse sensing?

Say I am southeast of the VOR station, and want to head straight to
that station in a northwest direction, at a heading of 300. I tune
and identify, and currently track the 300 radial (300 on the OBS),
with a "TO" indication, and the needle centered. If I wander to the
right of my course, the needle will swing to the left, so I'll turn a
few degrees to the left and rejoin the 300 radial.

First, am I tracking the 300 inbound radial or the 300 outbound
radial? What is the proper terminology?

Second, what if, instead of heading 300, I was heading 120. In other
words, what if I was heading in the exact reciprocal direction with
the OBS still at 300 and a "TO" indication? I assert that the needle
would still be centered; however, how would someone know that he's
indeed headed TOWARDS the station and not away from it?

Thanks!
Alex

Koopas wrote:
Hi all,

What is meant by reverse sensing?

Say I am southeast of the VOR station, and want to head straight to
that station in a northwest direction, at a heading of 300. I tune
and identify, and currently track the 300 radial (300 on the OBS),
with a "TO" indication, and the needle centered. If I wander to the
right of my course, the needle will swing to the left, so I'll turn a
few degrees to the left and rejoin the 300 radial.

First, am I tracking the 300 inbound radial or the 300 outbound
radial? What is the proper terminology?

You are tracking the 120 degree radial inbound. You don't have inbound or
outbound radials. You have radials, and you can be inbound or outbound on
one of them. You are on the 120 radial, not the 300 radial.


Second, what if, instead of heading 300, I was heading 120. In other
words, what if I was heading in the exact reciprocal direction with
the OBS still at 300 and a "TO" indication? I assert that the needle
would still be centered; however, how would someone know that he's
indeed headed TOWARDS the station and not away from it?

Because you'd have reverse sensing! Seriously, VORs have no idea which
way you're headed. Once you remember that, then things become easier. Now,
you are on the 120 radial headed AWAY from the VOR with 300 dialed in on the
OBS and you have a TO flag - because as far as the VOR receiver is
concerned, a 300 degree course would take you TO the VOR (remember, it
doesn't know which way you're going). Now, if you deviate to the right, the
needle will move to the RIGHT (reverse) because it thinks you're flying TO
the VOR and have deviated to the LEFT. That is reverse sensing. I don't
like the name cause it somehow implies the VOR is doing something
different - it isn't. It should be called "The pilot screwed up and dialed
in the wrong radial".

Hilton

(Koopas Ly) wrote in message . com...
Hi all,

What is meant by reverse sensing?

Say I am southeast of the VOR station, and want to head straight to
that station in a northwest direction, at a heading of 300. I tune
and identify, and currently track the 300 radial (300 on the OBS),
with a "TO" indication, and the needle centered. If I wander to the
right of my course, the needle will swing to the left, so I'll turn a
few degrees to the left and rejoin the 300 radial.



If you're Southeast of the station, and are flying toward the station,
it is the 120 degree radial you are flying, not the 300. The 300
radial only exists northwest of the VOR; the 120 exists southeast of
the VOR.

First, am I tracking the 300 inbound radial or the 300 outbound
radial? What is the proper terminology?


You are tracking the 120 degree radial; there is no
inbound/outbound distinction. VOR is a position instrument. The fact
that you are tracking the 120, with your OBS set at 300 is what
produces the "TO" flag on your omni head display.

Second, what if, instead of heading 300, I was heading 120. In other
words, what if I was heading in the exact reciprocal direction with
the OBS still at 300 and a "TO" indication? I assert that the needle
would still be centered; however, how would someone know that he's
indeed headed TOWARDS the station and not away from it?


If your OBS is set at 300, and you have a "TO" indication, and your
heading is 120, you are flying AWAY from the station.
This would be where the "Reverse sensing" you describe would take
place.
To track the radial, you would fly away from the needle.

Thanks!
Alex

Hope this Helps

Thomas Lembessis

ATP, F/E (B-727)

Koopas Ly wrote:

What is meant by reverse sensing?

Here's a site that may just change your life:

http://www.campbells.org/Airplanes/VOR/vor.html

Tim

"Greg Burkhart" wrote in message news:wh%_a.147370$o%2.63624@sccrnsc02...

You're correct. If you're SE of the VOR, a 300 TO will give you the correct
deflection if you're flying towards the VOR. If you do a 180° turn,

The easier way to think about it is to ignore "to/from" all together. If your
heading is the rougly the same as the OBS setting, then the left right indictions
of the needle will be normal. If you're heading is roughly the opposite of the
OBS setting then it's going to read backwards.

On 14 Aug 2003 23:18:27 -0700, (Koopas Ly)
wrote:

First, am I tracking the 300 inbound radial or the 300 outbound
radial? What is the proper terminology?

This assumes that you've positioned the OBS so that 300 is at the top
of the circle.

If the VOR says "TO" with the OBS set to 300 at the top, you're
positioned along the 120 radial, that is, you're southeast of the VOR
transmitter. Flying a heading of 300 will bring you TO the station,
flying 120 will fly you FROM the station. Notice here that the TOP of
the needle points to 300, and the BOTTOM points to 120.

If the VOR says "FROM" with the OBS set to 300 at the top, you're
positioned on the 300 radial, northwest of the transmitter. Flying a
heading of 120 will bring you TO the station, flying 300 will take you
FROM the station.

http://www.campbells.org/Airplanes/VOR/vor.html is what I read to make
sense of it all, after missing the questions on every FAA written
test. (thanks for posting it again, Tim; I had lost the link). After
going over that document I don't have problems using the VOR receivers
anymore at all.

Rob

Read this and then get back to us. It helped me tremendously. Good Luck.

http://www.campbells.org/Airplanes/VOR/vor.html

Jon Kraus
PP-ASEL
Student-IA


Koopas Ly wrote:

Hi all,

What is meant by reverse sensing?

Say I am southeast of the VOR station, and want to head straight to
that station in a northwest direction, at a heading of 300. I tune
and identify, and currently track the 300 radial (300 on the OBS),
with a "TO" indication, and the needle centered. If I wander to the
right of my course, the needle will swing to the left, so I'll turn a
few degrees to the left and rejoin the 300 radial.

First, am I tracking the 300 inbound radial or the 300 outbound
radial? What is the proper terminology?

Second, what if, instead of heading 300, I was heading 120. In other
words, what if I was heading in the exact reciprocal direction with
the OBS still at 300 and a "TO" indication? I assert that the needle
would still be centered; however, how would someone know that he's
indeed headed TOWARDS the station and not away from it?

Thanks!
Alex

"Koopas Ly" wrote in message
om...
Hi all,

What is meant by reverse sensing?

Say I am southeast of the VOR station, and want to head straight to
that station in a northwest direction, at a heading of 300. I tune
and identify, and currently track the 300 radial (300 on the OBS),
with a "TO" indication, and the needle centered. If I wander to the
right of my course, the needle will swing to the left, so I'll turn a
few degrees to the left and rejoin the 300 radial.


First, am I tracking the 300 inbound radial or the 300 outbound
radial? What is the proper terminology?


If you are SE of the VOR then you are not on the 300 radial. Think of
radials as "radiating" out from the VOR. In your case you are on the 120
radial inbound


Second, what if, instead of heading 300, I was heading 120. In other
words, what if I was heading in the exact reciprocal direction with
the OBS still at 300 and a "TO" indication? I assert that the needle
would still be centered; however, how would someone know that he's
indeed headed TOWARDS the station and not away from it?


If the needle was centered and you turn left and the needle goes left then
you would know that you are headed away from the VOR.

Thanks!
Alex

On Fri, 15 Aug 2003 16:50:25 GMT, Jeffrey Voight
wrote:

Here's a tip somebody told me, and it's worked for me:

When you see 'TO' think 'THROUGH'. That is, the 300 radial points all
the way 'THROUGH' the VOR. So, if you are on the 300 radial, CDI says
'TO (THROUGH)', you will fly 'THROUGH' the VOR station on a heading of 300.

When you see 'FROM' think, where is that signal coming 'FROM'? That is,
if I spin the dial on the CDI and it centers on 120 and FROM, that
signal is coming 'FROM' the VOR on a heading of 120.

The other thing he told me was that the only time I should see 'TO' is
when I'm trying to get 'TO' the VOR. The only time I should see 'FROM'
is when I'm trying to verify where I am (location fix). So, unless
you're headed for the VOR itself, you should see a FROM indication (and,
you should be drawing a line FROM the VOR on your map to fix your
location). If you want to fly TO the VOR (and subsequently beyond it),
you want to see TO on the CDI. Of course, once you've crossed the top
of the milk bottle, you won't be flying TO the VOR anymore. You'll now
just be verifying your position as you fly away FROM the station.
Perhaps you want to turn after you cross the VOR. You'll still want to
see FROM because no matter which way you turn, you'll still be flying
away FROM the VOR (unless, of course, you're turning back TO the VOR for
holding or just looking to get hit by other aircraft flying TO the VOR).

Jeff...

I like this explanation Jeff. I've looked at the Joe Campbell website
describing his method of interpreting VOR's and I have more trouble
with that than with the normally taught method of interpreting the
VOR.

It's a nice mnenomic: to, through.

My instructor gave me another one the other day regarding when winds
are true or magnetic. Devilishly difficult to remember for me
ordinarily until he said "if it's written, it's true". Therefore when
you hear it spoken, it's the other one, magnetic.

For me, the "if it's written it's true" mnemonic works great because
all my life I've heard people tell me that they've seen it written so
it must be true. Doesn't matter that extremely often the written word
is NOT true, the fact that I've heard it so often made it an instant
memory prod for me.

Corky Scott

I think the main thing that confuses people about VORs is
differentiating between location and course guidance. So let's
remove the couse guidance aspect for a moment:

Imagine you are in a helicopter in a stationary hover pointed
at 360 magnetic. You tune in a VOR and set the OBS to 360. The needle
deflects full left. What does this mean? It means that the imaginary
line starting a the VOR and radiating out (hence "radial") toward the
magentic north pole is located somewhere to your left. Now you do a
180-degree pedal turn so your helicopter is pointed at 180 degrees.
What will happen to the CDI needle? Nothing, because you are stationary.
It will still be deflected full left. However, because you have turned
180 degrees, the radial is now actually to your right. THAT is reverse
sensing.

Another way to think of it is the CDI needle tells you which
direction you need to turn the OBS in order to center the needle.

So now you push the cyclic forward and start your helicopter moving.
You now want to use your CDI for course guidance. If your current
heading is within +/- 90 degrees of your OBS setting, the CDI needle
will be a "command instrument", i.e. it will tell you which direction
to turn in order to intercept the selected radial. If your current
heading is MORE than +/- 90 degrees from your current OBS setting,
then you must turn in the opposite direction of the needle to intercept.

So what about the TO/FROM flag? Your OBS is still set to 360. Now
draw a line perpendicular to 360 passing through the VOR. The TO/FROM
flag can tell you on which side of this perpendicular line you are
located. Like the OBS setting, the TO/FROM flag is NOT related to
what direction your aircraft is pointed. If the flag is indicating
FROM, then you are on the same side of the perpendicular line as the
360 radial. An indication of TO means you are on the opposite side
of the line.


Happy landings,
Ross Oliver